drm: sti: add bindings for DRM driver

Add DRM/KMS driver bindings documentation.
Describe the required properties for each of the hardware IPs drivers.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Reviewed-by: Rob Clark <robdclark@gmail.com>

1 files changed, 58 insertions, 0 deletions

diff --git a/drivers/gpu/drm/sti/NOTES b/drivers/gpu/drm/sti/NOTES
new file mode 100644
index 0000000..57e2579
--- /dev/null
+++ b/drivers/gpu/drm/sti/NOTES
@@ -0,0 +1,58 @@
+1. stiH display hardware IP
+---------------------------
+The STMicroelectronics stiH SoCs use a common chain of HW display IP blocks:
+- The High Quality Video Display Processor (HQVDP) gets video frames from a
+  video decoder and does high quality video processing, including scaling.
+
+- The Compositor is a multiplane, dual-mixer (Main & Aux) digital processor. It
+  has several inputs:
+  - The graphics planes are internally processed by the Generic Display
+    Pipeline (GDP).
+  - The video plug (VID) connects to the HQVDP output.
+  - The cursor handles ... a cursor.
+- The TV OUT pre-formats (convert, clip, round) the compositor output data
+- The HDMI / DVO / HD Analog / SD analog IP builds the video signals
+  - DVO (Digital Video Output) handles a 24bits parallel signal
+  - The HD analog signal is typically driven by a YCbCr cable, supporting up to
+    1080i mode.
+  - The SD analog signal is typically used for legacy TV
+- The VTG (Video Timing Generators) build Vsync signals used by the other HW IP
+Note that some stiH drivers support only a subset of thee HW IP.
+
+                  .-------------.   .-----------.   .-----------.
+GPU >-------------+GDP     Main |   |           +---+    HDMI   +--> HDMI
+GPU >-------------+GDP     mixer+---+           |   :===========:
+GPU >-------------+Cursor       |   |           +---+    DVO    +--> 24b//
+        -------   |  COMPOSITOR |   |  TV OUT   |   :===========:
+       |       |  |             |   |           +---+ HD analog +--> YCbCr
+Vid >--+ HQVDP +--+VID     Aux  +---+           |   :===========:
+dec    |       |  |        mixer|   |           +---+ SD analog +--> CVBS
+       '-------'  '-------------'   '-----------'   '-----------'
+                   .-----------.
+                   |       main+--> Vsync
+                   | VTG       |
+                   |        aux+--> Vsync
+                   '-----------'
+
+2. DRM / HW mapping
+-------------------
+These IP are mapped to the DRM objects as following:
+- The CRTCs are mapped to the Compositor Main and Aux Mixers
+- The Framebuffers and planes are mapped to the Compositor GDP (non video
+  buffers) and to HQVDP+VID (video buffers)
+- The Cursor is mapped to the Compositor Cursor
+- The Encoders are mapped to the TVOut
+- The Bridges/Connectors are mapped to the HDMI / DVO / HD Analog / SD analog
+
+FB & planes         Cursor      CRTC     Encoders    Bridges/Connectors
+   |                   |          |         |                       |
+   |                   |          |         |                       |
+   |              .-------------. | .-----------.   .-----------.   |
+   +------------> |GDP |   Main | | |       +-> |   |    HDMI   | <-+
+   +------------> |GDP v   mixer|<+ |       |   |   :===========:   |
+   |              |Cursor       | | |       +-> |   |    DVO    | <-+
+   |    -------   |  COMPOSITOR | | |TV OUT |   |   :===========:   |
+   |   |       |  |             | | |       +-> |   | HD analog | <-+
+   +-> | HQVDP |  |VID     Aux  |<+ |       |   |   :===========:   |
+       |       |  |        mixer|   |       +-> |   | SD analog | <-+
+       '-------'  '-------------'   '-----------'   '-----------'